2015年3/4月GMAT機經：閱讀部分（四）

　　網GMAT頻道小編第臨時間為列位考生整頓了2015年3/4月GMAT瀏覽部門機經，以供門生們參考!

　　4. 生物鏈與毒素積聚【考古待確認】

　　【原始】

　　一些毒物會跟著生物鏈積累。越高真個檢測到越多。生存在水裏的動物lung可以協助疏散一些。但當陸地震物等也介入到食品鏈就不同樣了…考古吧…

　　【考古】

　　V1. P1先先容了toxin可以經由過程食品鏈賡續往食品鏈頂端累計，然後似乎說了一個試驗，彪炳一個甚麽結論，然則這個試驗只是針對水裏的動物的。P2就開端說however上面的試驗沒有包括陸活潑物，然後剖析了一通關於化學物資汙染物啥的跟水生陸活潑物的幹系。

　　V2. 【疑似原文，待確認】

　　hyukhee 已將文章舉行了翻譯,同窗們可以直接看文章背面的中文翻譯啦~~~

　　Biomagnification 有毒化學物資在食品鏈各個關鍵中的毒性漸進 means that the level of toxin in animals' tissues rises as one moves up the food chain. For instance, as larvae eat algae, (此處 有題 問 algae 的感化,我選的是處在食品鏈最低端~~不知對否~) fish eat the larvae, and bigger fish eat smaller fish, the toxin present in the algae becomes increasingly concentrated; top predators like swordfish and polar 由於處在食品鏈頂端以是毒素最高 bears end up with the highest doses in their tissues. This can happen with stable, fat-soluble 脂溶性的 chemicals that aren't easily excreted in urine or feces 不易經由過程尿或糞便滲出出去. Biomagnification was first studied in the late 1960s in aquatic 水上的 food webs, explains Frank Gobas, professor at Simon Fraser University and leader of the study. To screen chemicals, scientists began using a property known as Kow 水分派系數, which indicates how readily a chemical dissolves in water compared with fat and thus predicts how easily it will move from a fish's blood lipids into water through its gills 鰓. Low-Kow, or more water soluble 可消融的, chemicals don't build up in the fish food chain and were assumed to be safe. Gobas 這小我第一個發明了這類化學物資可以在水中消融,魚 可以很輕易地經由過程鰓來滲出。Gobas 一開端以為 low-Kow 平安。

　　Environmental chemists realized, however , that this assumption might not hold in food chains involving mammals and birds because their lungs are in contact with air, not water. This means that many chemicals that are relatively soluble in water and therefore don't accumulate in fish might remain in the tissues of land animals if they aren't volatile enough to easily move from the lungs into the air (predicted by a property called Koa 氛圍分派系數). Supporting this idea, some organic chemicals that don't biomagnify in fish appeared to be doing so in other wildlife and humans. 然則,情況學家以為這個假如紕謬,提出哺乳動物和鳥類大概不克不及滲出這類化學毒 素,由於它們的肺打仗氛圍而不是水。Koa

　　To explore this hypothesis, Gobas and graduate student Barry Kelly and colleagues collected plant and animal tissue samples— from lichens 青苔 to beluga 白鯨 whales killed in Inuit hunts—in the Arctic, where, because of weather patterns and cold temperatures, organic pollutant levels are high. They tested the samples not only for known POPs but also for several chemicals with a low Kow but high Koa, which suggested they might biomagnify in air-breathing animals. The measured levels of contaminants for various animals in aquatic and land food webs were similar to those predicted from a bioaccumulation model incorporating 歸並一體化 Koa and Kow, suggesting the model was correct. Chemicals with low Kow and high Koa stood out as potentially risky. 末了 Gobas 也說 Low Kow 而且 high Koa 的有潛伏傷害的,證明了 Biomagnification,即 毒素跟著食品鏈的增加會沉積。毒素最低

　　附:感激 hyukhee 童鞋供給的翻譯

　　B 是指毒素經由過程動物構造沿著食品鏈挪動。比方,幼蟲 larvae 吃海藻 algae,魚吃幼蟲,大魚吃小魚,毒素在海藻中的含量增長,頂層的如 swordfish 和 polar bears 的掠食者積聚至多。 這(化學物資在掠食者中積聚)是穩固的,由於脂溶性的 fat-soluble 化學物資不易經由過程尿 urine 或糞便 feces 滲出出去。第一次發明 B 是在 1960s SFU 的傳授 Frank Gobas 研討水中食 物網的時刻。為了反應化學物資,科學家開端應用 KOW 來視察含脂肪的化學物資是如安在水中消融的,而且可以猜測這類化學物資怎樣經由過程魚的腮 gill,從魚的血液裏流入水中。 Low-Kow 解釋這類水溶性的化學物資不影響魚的食品鏈,而且是很平安的。

　　然則,情況化學家發明,這個假如在 mammal 和 bird 的食品鏈中不可立,由於他們是靠肺 lung 和 air 打仗的,不是靠水。這就象征著很多水溶性的化學物資不可以或許在魚的體內積聚, 卻可以或許在陸地震物的體內積聚,假如他們不易揮發的話(可以用 Koa 來猜測)。以是,一 些不在魚中舉行 B 的化學物資卻可以在其他野活潑物和人類中舉行 B。(便是可以在 mammal 和 bird 的食品鏈中轉移毒素)

　　為了摸索這個假如,Gobas 和他的門生 Barry Kelly 另有同事們網絡了植物和動物的構造樣本 ——從青苔 lichens 到白鯨 beluga whales——在北極,因為其氣象和低溫,器官內的汙染物資 (毒素)會積聚許多。他們測試這些樣本不單單是為了曉得 POPs,還為了找到一些 low Kow 然則 high Koa 的化學物資,這些化學物資象征著在 air-breathing animals 中有 B。分歧動物, 水大概陸地,的食品網中汙染物資含量和歸並 Koa and Kow 猜測的成果類似,解釋這個模子 是準確的。low Kow and high Koa 的化學物資有潛伏的危害。